Use of novel virulence-specific genes as targets for diagnosis and potential control of virulent strains of listeria monocytogenes

ABSTRACT

A method for identifying virulent strains of  L. monocytogenes  that includes the use of primers or probes in a PCR assay or hybridization technique that employs primers or probes, which are specific for virulence-specific genes of  L. monocytogenes . Also provided is a method of control of  L. monocytogenes  strains that have been identified using the method of the present invention.

[0001] This application claims priority from U.S. Provisional Application Ser. No. 60/444,201, filed Feb. 3, 2003; U.S. Provisional Application Ser. No. 60/447,297, filed Feb. 14, 2003; and U.S. Provisional Application Ser. No. 60/458,414, filed Mar. 31, 2003. The entirety of each of these provisional applications is incorporated herein by reference.

[0002] This invention was made with Government support under 58-0790-0-120 awarded by the U.S. Department of Agriculture-Agricultural Research Service. The Government may have certain rights in the invention.

BACKGROUND OF THE INVENTION

[0003] 1. Field of the Invention

[0004] This invention involves the use of novel virulence-specific genes of Listeria monocytogenes as targets for specific diagnosis and potential control of virulent strains of L. monocytogenes. More particularly, this invention provides a PCR or hybridization method, which uses specific primers or probes corresponding to virulence-specific genes for the identification and control of virulent strains of Listeria monocytogenes.

[0005] 2. Background of the Technology

[0006]L. monocytogenes is an important cause of human food borne diseases world wide. A notable feature of L. monocytogenes is that it shows considerable variation in its ability to produce listeriosis. On the one extreme, some L. monocytogenes strains are virulent and can result in severe disease and mortality. On the other, some have limited capability to establish in the host and are relatively avirulent and harmless. Because manufactured food products detected with L. monocytogenes are recalled or downgraded (i.e., used for pet food), contamination with this species may render significant economic losses. With outbreaks of listeriosis due to contaminated foods on the increase in recent years, L. monocytogenes has become a major concern to the food industry and health regulation authority.

[0007] Apart from adapting stringent quality control measures during food processing procedures, frequent monitoring with specific laboratory tests for virulent strains of L. monocytogenes is vital in reducing unnecessary food product recalls and allaying consumer concerns. The current diagnostic methods are incapable of distinguishing virulent from avirulent strains of L. monocytogenes.

[0008] The complete genome of Listeria monocytogenes EGDe strain was reported recently (Glaser et al., 2001). Although this publication contains a list of all known and putative genes in L. monocytogenes EGD strain as well as their nucleotide sequences, it does not provide any information on the actual application of these genes. Therefore, although the DNA sequences of the genes described in this invention have been published and are in public domain through the release of the L. monocytogenes EGDe genome sequence, there are no prior publications on the functions of these genes or on their use for research or diagnostic purposes.

[0009] Previous research used PCR and DNA sequencing or restriction fragment length polymorphism of the L. monocytogenes hlyA, actA, and inlA genes to group L. monocytogenes into three genetic lineages, with the various lineages varying in potential for human virulence (Norton et al., 2001; Wiedmann et al., 1997). Ribotyping (sequencing of rRNA genes) was also used in this research. These assays are different from the present assay employed by the inventors in that they require either DNA sequencing or restriction digests following PCR amplification, while the present assay is simply a PCR assay. In addition, the hlyA, actA, and inlA genes are present in all L. monocytogenes isolates, while the virulence-specific genes described by the inventors are found only in virulent strains of L. monocytogenes.

[0010] Another PCR assay, random amplification of polymorphic DNA (RAPD) PCR, has been used to classify L. monocytogenes into genetic groups that tend to predict virulence. This technique is based on the use of nonspecific primers that bind to unknown sequences in the L. monocytogenes chromosome (Franciosa et al., 2001). The PCR assay employed by the inventors is based on primers that bind to specific virulence associated chromosomal sequences that we have identified.

[0011] Other assays have been described for differentiation of virulent and avirulent L. monocytogenes isolates. The “gold standard” for virulence testing of L. monocytogenes isolates is the mouse virulence test. This test is expensive, labor intensive, requires several weeks to complete, and requires regulatory approval to ensure humane treatment of animals. Assays have been described based on cell culture models; one correlated L. monocytogenes virulence with the ability of isolates to form plaques on HT-29 cells (Roche et al., 2001), and another correlated virulence with the ability to cause cytopathogenic effects in Caco-2 cells (Pine et al., 1991). Although the use of cell culture models represents an improvement over mouse virulence testing, it is still time-consuming and labor intensive.

[0012] Research has been published on the use of phenotypic detection of virulence factor expression (listeriolysin, phosphatidylinositol phospholipase C, phosphatidylcholine phospholipase C) to separate virulent from avirulent L. monocytogenes isolates (Erdenlig et al., 2000). Research has also been published on the use of monoclonal antibodies for detection of virulence factor expression (listeriolysin and phosphatidylcholine phospholipase C) to distinguish virulent and avirulent isolates (Erdenlig et al., 1999). The dot blot hybridization technique described in this invention has also been previously published. For example, this technique was employed to identify virulence and avirulence associated markers of Dichelobacter nodosus—the ovine footrot pathogen (Liu & Yong, 1993). Several PCR assays have been described for species specific detection of L. monocytogenes (examples include Aznar & Alarcon, 2002; Bassler et al., 1995; Blais et al., 1997; Klein & Juneja, 1997; Norton & Batt, 1999; Winters et al., 1999). PCR assays for distinguishing all six Listeria species can be based on the 16S and 23S rRNA genes (Sallen et al., 1996) or the intergenic spacer region of 16S and 23S rRNA genes (Graham et al., 1997), or the iap gene (Bubert, et al., 1999). However, none of these PCR assays distinguish virulent L. monocytogenes isolates from avirulent isolates.

SUMMARY OF THE INVENTION

[0013] This invention involves the use of virulence-specific genes of Listeria monocytogenes as targets for specific diagnosis and potential control of virulent strains of L. monocytogenes and overcomes the above identified shortcomings of conventional detection methods.

[0014] Using a comparative screening strategy, the inventors isolated two potential virulence-specific clones from a recombinant DNA library from L. monocytogenes strain EGD. Specifically, a hybridization technique was used to compare genomic DNA from virulent and avirulent L. monocytogenes isolates to identify clones containing genetic markers that are uniquely present in either virulent and/or avirulent strains. DNA sequence analysis of the two virulence specific clones revealed that they contain gene markers that are distinct from the previously reported virulence gene cluster encompassing prƒA, plcA, hlyA, mpl, actA, and plcB. By employing primers derived from these as well as other newly identified virulence-specific gene markers, the inventors discovered a method by which virulent strains of L. monocytogenes can now be readily distinguished from avirulent strains through the formation of specific PCR products.

[0015] The method of the present invention for separation of virulent and avirulent L. monocytogenes isolates can be used to provide a scientific basis for the determination of when and if food safety recalls should occur when L. monocytogenes is isolated from food products.

[0016] In one embodiment of this invention, virulence-specific genes of Listeria monocytogenes are used as targets for specific diagnosis and potential control of virulent strains of L. monocytogenes.

[0017] In another embodiment of this invention, one or more of L. monocytogenes virulence-specific genes are used to detect virulent strains of L. monocytogenes.

[0018] In another embodiment of this invention, one or more of L. monocytogenes virulence-specific genes are used to detect virulent strains of L. monocytogenes by polymerase chain reaction (PCR) using primers specific for the DNA sequence from the gene(s) or by hybridization using a probe specific for the DNA sequence from the gene(s).

[0019] In another embodiment of this invention, the one or more L. monocytogenes virulence-specific genes are selected from the group consisting of: lmo0833, lmo2672, lmo1116, and lmo1134 (encoding putative transcriptional regulators); lmo0834 and lmo1188 (encoding proteins with unknown function); and lmo0333, lmo2470, and lmo2821 (encoding proteins similar to internalins).

[0020] In another embodiment of this invention, a combination of two or more of L. monocytogenes virulence-specific genes are used to detect virulent strains of L. monocytogenes by multiplex polymerase chain reaction (PCR) or hybridization using primers or probes specific for the DNA sequences from the gene(s).

[0021] In another embodiment of this invention, one or more of L. monocytogenes virulence-specific genes are used to detect virulent strains of L. monocytogenes by multiplex polymerase chain reaction (PCR) or hybridization using primers or probes specific for the DNA sequence from the gene(s) in combination with Listeria genus-specific primers or probes and/or L. monocytogenes species-specific primers or probes.

[0022] In another embodiment of this invention, the one or more L. monocytogenes virulence-specific genes are one or more genes that indicate virulent forms of L. monocytogenes or combinations thereof.

[0023] In another embodiment of this invention, the L. monocytogenes virulence-specific genes or their derivatives are used in the inhibition of growth, reduction of pathogenicity, treatment, or prevention of virulent strains of Listeria monocytogenes.

[0024] In another embodiment of this invention, virulent strains of Listeria monocytogenes are detected by amplification of L. monocytogenes virulence-specific genes from mRNA by reverse transcription-PCR (RT-PCR).

[0025] In another embodiment of this invention, virulent strains of Listeria monocytogenes are detected by one or more methods for detection of protein product(s) from L. monocytogenes virulence-specific genes.

[0026] In another embodiment of this invention, virulent strains of Listeria monocytogenes are detected by one or more methods for detection of protein product(s) from L. monocytogenes virulence-specific genes using either polyacrylamide gel electrophoresis, high-performance liquid chromatography (HPLC), mass spectrometry, or antibody detection methods (examples include immunofluorescent antibodies (IFA), enzyme-linked immunosorbent assay (ELISA), or Western blotting).

[0027] In another embodiment of this invention, virulent strains of Listeria monocytogenes are detected by one or more methods for detection of protein product(s) from L. monocytogenes virulence-specific genes by use of assay(s) specific for the function(s) of the protein product(s).

[0028] In another embodiment of this invention, the virulence-specific L. monocytogenes genes are used as a treatment strategy such that pharmaceutically active agent(s) would inactivate or alter the function of one or more of the proteins encoded by the virulence-specific L. monocytogenes genes, which would either kill the virulent L. monocytogenes or render it susceptible to the host immune system.

[0029] In another embodiment of this invention, one or more of the L. monocytogenes genes or promoter(s) for one or more of the virulence-specific L. monocytogenes genes is altered such that expression of the encoded protein(s) would be completely disrupted or altered. The said alteration or disruption of expression would render L. monocytogenes avirulent and effective as a live attenuated vaccine.

[0030] In another embodiment of this invention, the L. monocytogenes virulence-specific genes are selected from the group consisting of: lmo0833, lmo1188, lmo0834, lmo1116, lmo2672, lmo1134, lmo1333, lmo2470, and lmo2821.

[0031] In another embodiment of this invention, the one or more L. monocytogenes virulence-specific genes are one or more genes that indicate one or more virulent forms of L. monocytogenes.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032]FIG. 1 shows the DNA sequences of SEQ ID NOS.: 1-9 for each of the virulence-specific genes of Listeria monocytogenes according to the present invention.

[0033]FIG. 2 shows the DNA sequences of SEQ ID NOS.: 28-33 for each of the Listeria species-specific gene sequences according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0034]Listeria monocytogenes is a small gram-positive coccobacillus that tends to form short chains of three to five bacteria. Infections from this pathogen occur worldwide in various animals and man (Gray and Killinger, 1966) and can be fatal in immunocompromised individuals such the elderly, pregnant women, newborns, diabetics and transplantation patients (Gellin and Broome, 1989). L. monocytogenes is of particular concern to the food industry and public health regulatory agencies because it can grow at refrigerator temperatures and because it is ubiquitous in nature (Farber and Speirs, 1987, Lamont et al., 1988). It has been found in a variety of foods such as vegetables (Heisick et al., 1989), milk (Donnelly and Baigent, 1986, Doyle et al., 1987), various cheeses (Rodler and Korbler, 1989), meat products (Farber et al., 1989), poultry (Carpenter and Harrison, 1989), and fish (Lennon et al., 1984; Erdenlig et al., 1999). Of the 13 known serotypes of L. monocytogenes, many of which are found in foods, only three serotypes (1/2a, 1/2b, 4b) are associated with the majority of human illness (Schuchat et al., 1991). However, not all strains of these L. monocytogenes serotypes are pathogenic, with some strains having either no or low-level virulence (Hof and Rocourt, 1992). Previous work at the College of Veterinary Medicine at Mississippi State University indicated that L. monocytogenes isolates from channel catfish vary in virulence using the mouse model, with some isolates being highly virulent and others being completely avirulent (Erdenlig et al., 2000). There is also molecular evidence for the existence of genetic lineages of L. monocytogenes that vary in virulence (Norton et al., 2001; Wiedmann et al., 1997). This data indicates that food safety recalls based solely on detection of L. monocytogenes without determination of virulence could lead to unnecessary recalls, which would have devastating consequences on food producers and processors. To prevent economic losses due to food recalls, and to reduce human food safety concerns, it is important to understand what causes certain L. monocytogenes to be virulent and to devise ways to accurately ascertain virulence.

[0035]L. monocytogenes is a facultative intracellular pathogen, and some of its best-known virulence factors contribute to its ability to survive inside professional phagocytic cells. After it is phagocytosed, L. monocytogenes lyses the host vacuole and escapes into the cell cytoplasm. This step is mediated by listeriolysin (LLO) and phosphatidylinositol phospholipase C (PI-PLC) (Camilli et al., 1993, Portnoy et al., 1988). The bacteria are then propelled through the host cell cytoplasm by inducing the polymerization of host actin, a process that is mediated by a surface protein designated ActA (Domann et al., 1992). The bacteria then apparently spread from cell to cell by inducing formation of pseudopod-like structures containing bacteria that are internalized by neighboring cells. A second phospholipase, phosphatidylcholine phospholipase C (PC-PLC) is required for this step (Vazquez-Boland et al., 1992). A zinc metalloprotease, Mpl, may be required for activation of PC-PLC (Poyart et al., 1993).

[0036] The genes encoding these virulence factors are clustered on the L. monocytogenes chromosome between the ldh and prs operons: prfA (PrƒA, regulatory gene), plcA (PI-PLC), hlyA (LLO), mpl (Mpl), actA (ActA), and plcB (PC-PLC) (Portnoy et al., 1992). This gene cluster is one of the most well studied regions of the L. monocytogenes chromosome; there have been numerous publications on the roles that these genes play in virulence (Bohne et al., 1996, Bubert et al., 1999, Freitag and Jacobs, 1999, Kuhn and Goebel, 1995, Smith et al., 1995).

[0037] Previous work at the College of Veterinary Medicine at Mississippi State University has shown that expression of LLO and PC-PLC is valuable in indicating the pathogenicity of L. monocytogenes isolates (Erdenlig et al., 1999; Erdenlig et al., 2000). Expression of LLO and PC-PLC in seven L. monocytogenes isolates were compared, four of which were virulent in mice and three of which were avirulent in mice. Expression of both LLO and PC-PLC was present in all four virulent strains, and expression of LLO and PC-PLC was absent in two out of three avirulent strains (Table 1). None of the three avirulent strains expressed both LLO and PC-PLC. TABLE 1 Application of mAbs to detect the presence of virulence factors from L. monocytogenes channel catfish isolates and their correlation to pathogenicity L. monocytogenes catfish isolate Serovar LLO PC-PLC Pathogenicity¹ ATCC 15313 1 − + − ATCC 19115 4b + + + EGD ½a + + + CCF 1² 1 + + + HCC 7² 1  +³ + + HCC23 4 + − −

[0038] DNA sequencing of the promoters from the virulence gene clusters of these seven L. monocytogenes isolates were completed. The promoters that were sequenced control expression of the hlyA, plcA, prƒA, and plcB genes. In addition, the entire prƒA gene was sequenced from the seven isolates because PrfA binds to each of these promoters to control transcription. The sequences were obtained by first amplifying the regions of interest by PCR and directly sequencing the PCR products.

[0039] The sequencing results provide evidence that there are distinct genetic lineages of L. monocytogenes based on the virulence gene promoter sequences. Phylogenetic analysis indicated that in three of the promoters, the seven strains grouped consistently into three genetic lineages. In the fourth promoter controlling hly (LLO) expression, five out of seven isolates were grouped into the same genetic lineages. The different groupings of the other two strains at this promoter possibly reflect differences in expression of LLO.

[0040] The sequencing results also revealed potential sequence differences that could explain the differential expression of LLO and PC-PLC between isolates. In one isolate that fails to express PC-PLC, two amino acid substitutions were detected in PrfA. In the hly promoter, there were three nucleotide substitutions in the strain that fails to produce LLO compared to other strains. In one of the plcB promoters, there were four nucleotide substitutions in the promoter region of a non-PC-PLC producing strain compared to other strains.

[0041] However, the sequencing results also demonstrated that these genes (prƒA, plcA, hlyA, and plcB) are not good candidates for the development of PCR-based tests for distinguishing virulent from avirulent strains. These genes are present in all L. monocytogenes isolates (and even some other Listeria species), and the sequencing results demonstrated that the sequence variations in these genes between virulent and avirulent isolates are too few to allow development of PCR primers that would reliably distinguish virulent and avirulent isolates.

[0042] Therefore, the goal was to identify other gene markers that could be used for distinguishing virulent L. monocytogenes isolates from avirulent isolates. Although the genome sequence of virulent L. monocytogenes strain EGD recently became available (Glaser et al., 2001), the sequence of avirulent L. monocytogenes isolates are not available for comparison to identify these unique genes. Therefore, dot blot hybridization was used to identify L. monocytogenes virulence-associated markers, which is a technique that had been previously used to detect chromosomal markers that are unique to both virulent and avirulent isolates of Dichelobacter nodosus, the causative agent of ovine footrot (Liu and Yong, 1993). These markers identified from D. nodosus were used as the basis for development of a diagnostic test that can be used to differentiate virulent, intermediate, and avirulent isolates of this species (Liu, 1994).

[0043] To prepare for dot blot hybridization, genomic DNA was prepared from the known virulent and avirulent strains of Listeria monocytogenes using a standard protocol (Ausubel et al., 1994) and suspended in TE buffer (10 mM Tris, 1 mM EDTA, pH 8.0). The purified DNA from virulent strain EGD and avirulent strain HCC23 was partially digested with restriction endonuclease Sau3A I. Digested DNA was separated by agarose gel electrophoresis, and fragments in the 0.5-3 kilobase range were excised and eluted. The size fractionated DNA was then cloned into BamH I digested plasmid vector (pGEM-3Z; Promega). The resultant recombinant DNA libraries were transformed into E. coli XL1-Blue MRF, and clones with insert were identified by blue-white screening. Plasmid DNA was isolated from individual clones in batches of 50 using a rapid alkaline lysis procedure. Inserts were isolated by digestion with Pst I and EcoR I, separated from vector DNA by agarose gel electrophoresis, eluted by the phenol-thaw method, and labeled for hybridization using the ECL protocol for labeling double stranded DNA (Amersham Pharmacia Biotech). If inserts contained Pst I or EcoR I restriction sites, inserts were recovered by digestion with Sma I and Hind III.

[0044] The dot blot hybridization was conducted using the procedure described by Liu and Yong (Liu and Yong, 1993). Briefly, DNA from each of the four virulent strains and the three avirulent strains were heated at 100° C. for 3 minutes before being mixed with an equal volume of 1.8 M NaCl, 0.18 M sodium citrate and 4.4 M formaldehyde. Fifty microliters of DNA from each of the seven strains (0.5 g DNA/dot) was spotted onto nylon membranes (Hybond-N, Amersham Pharmacia Biotech) using a dot blot apparatus (Schleicher and Schuell). DNA was spotted in 50 panels, with each panel containing one dot from each of the seven strains, and fixed on membranes using UV light in a Stratalinker 2400 (Stratagene). Dot blot panels were separated from each other and individually hybridized with the labeled inserts.

[0045] Inserts were identified from these hybridizations that demonstrate preferential binding to virulent or avirulent strains. Inserts from identified clones were sequenced on both ends using primers from the vector sequence. Clones from the virulent strain EGD were easily identified based on the available genome sequence data, but inserts from the avirulent strain required sequencing the entire insert using a primer walking strategy. Southern hybridizations using labeled probes from the identified clones were conducted using genomic DNA from all seven strains to confirm results from the dot blot hybridizations.

[0046] Through this comparative screening procedure, two recombinant clones (Lmo2-28 and Lmo2-432) were identified from the genomic DNA libraries of L. monocytogenes strain EGD (NCTC7973). Following nucleotide sequence analysis of these two clones and subsequent BLAST searches at GenBank, clone Lmo2-28 was found to contain parts of lmo0833lmo0834 of L. monocytogenes EGDe, which encode a putative transcriptional regulator and an unknown protein. Clone Lmo2-432 was found to contain part of lmo1188 of L. monocytogenes EGDe, which encodes an unknown protein. Because of this interesting finding and the fact that transcriptional regulators are specialized DNA binding proteins that play essential roles in the regulation of RNA synthesis and gene expression within bacteria, attention was focused on genes encoding transcriptional regulators in L. monocytogenes. As a result, several other genes (lmo2672, lmo1116, and lmo1134) were selected from the list of L. monocytogenes EGDe genes (Glaser et al., 2001) for further evaluation (Table 2). Furthermore, because internalins are found exclusively in Listeria, additional attention was also directed to L. monocytogenes EGDe genes that encode putative internalins. Thus, the inventors selected three genes (lmo0333, lmo2470, and lmo2821) that code for proteins similar to internalins for assessment. The Listeria monocytogenes virulence-specific genes used as examples of the present invention are listed in Table 2. Sequence lists for each of these genes are shown in FIG. 1 as: lmo0833 (SEQ ID NO: 1), lmo1188 (SEQ ID NO: 2), lmo0834 (SEQ ID NO: 3), lmo1116 (SEQ ID NO: 4), lmo2672 (SEQ ID NO: 5), lmo1134 (SEQ ID NO: 6), lmo0333 (SEQ ID NO: 7), lmo2470 (SEQ ID NO: 8), and lmo2821 (SEQ ID NO: 9). Primers [forward primers (5′-3′) and reverse primer (3′-5′)], corresponding to each of the L. monocytogenes virulence-specific genes are also shown in Table 2. As indicated in the Table, these primers are sequentially designated as SEQ ID NOS.: 10-27. The oligonucleotide primers, which were designed from each of these genes were assessed in PCR against a collection of 29 L. monocytogenes strains (Table 3). TABLE 2 Identities of novel L. monocytogenes virulence specific gene markers PCR Genome Putative Size Forward primer Reverse primer Primer product Gene location function (aa) (5′-3′) (5′-3′) positions (bp) lmo0833 223780- Transcrip- 296 ggctattctttagcggagga agtagcgcgagggatttgta 223996-224015; 638 224730 tional SEQ ID NO. 10 SEQ ID NO. 11 224633-224613 regulator lmo1188 53621- Unknown 483 tttcgccgttagaaaatacga ttcggacaaaaatttgaatgg  54027-54047; 663 55085 protein SEQ ID NO. 12 SEQ ID NO. 13  54689-54668 lmo0834 224810- Unknown 237 aacttcgcatttgttatgtgttac tcactgaccattcctccaaa 224940-224963; 594 225537 protein SEQ ID NO. 14 SEQ ID NO. 15 225533-225513 lmol1116 262997- Transcrip- 257 gggaacgatgaaaacgaaga tggcttatcgcacaagctaat 263006-63025; 591 263783 tional SEQ ID NO. 16 SEQ ID NO. 17 263593-263573 regulator lmo2672 25985- Transcrip- 268 cggcacacttggattctcat agggctagtgacggatgcta  26117-26136; 481 26804 tion SEQ ID NO. 18 SEQ ID NO. 19  26597-26578 regulator lmo1134 8009- Transcrip- 115 acccgatagcaaggaggaac aacttctctcgatacccatcca  7998-8017; 367 8368 tional SEQ ID NO. 20 SEQ ID NO. 21  8364-8343 regulator lmo0333 936- Internalin 1778 ccgatttagaaacgcttgga ttcggcatatcgtgaatcat  1930-1949; 640 6272 SEQ ID NO. 22 SEQ ID NO. 23  2569-2550 lmo2470 149254- Internalin 388 tgattccatgcaattactagaacg aggattctaaactaggtaagtt 149527-149550; 545 150433 SEQ ID NO. 24 ggtg 150071-150046 SEQ ID NO. 25 lmo2821 188153- Internalin 851 tgtaaccccgcttacacagtt ttacggctggattgtctgtg 188989-189009; 611 190708 SEQ ID NO. 26 SEQ ID NO. 27 189599-189580

[0047] TABLE 3 List of bacterial strains examined by PCR using L. monocytogenes virulence specific primers lmo0833/ lmo2672/ Strain Serovar lmo1188 lmo0834 lmo1116 lmo1134 lmo0333 lmo2470 lmo2821 L. monocytogenes ATCC 19111 1 + + + + + + + L. monocytogenes ATCC 19112 2 + + + + + + + L. monocytogenes ATCC 19113 3 + + + + + + + L. monocytogenes ATCC 19114 4a − − − − − − − L. monocytogenes ATCC 19115 4b − + − + + + + L. monocytogenes ATCC 19116 4c − − + − − − + L. monocytogenes ATCC 19117 4d − + + + − + + L. monocytogenes ATCC 19118 4e − − + + − + + L. monocytogenes ATCC 15313 1 + − + + − + + L. monocytogenes EGD (NCTC 7973) ½a + + + + + + + L. monocytogenes HCC7 1 + + + + + + + L. monocytogenes HCC8 1 + + + + − + + L. monocytogenes HCC12 4 − − − − − − − L. monocytogenes HCC13 4 − − − − − − − L. monocytogenes HCC16 4 − − − − − − − L. monocytogenes HCC17 4 − − − − − − − L. monocytogenes HCC18 4 − − − − − − − L. monocytogenes HCC19 4 − − − − − − − L. monocytogenes HCC23 4 − − − − − − − L. monocytogenes HCC24 4 − − − − − − − L. monocytogenes HCC25 4 − − − − − − − L. monocytogenes 168 + + + + + + + L. monocytogenes 180 +/− + − + + + + L. monocytogenes 418 + + − + + + + L. monocytogenes 742 + + + + + + + L. monocytogenes 874 − − − − + + + L. monocytogenes 1002 + + + + + + + L. monocytogenes 1084 + + + + − + + L. monocytogenes 1400 + + + + + + + L. innocua ATCC 33090 6a − − − − − − − L. innocua 415 − − − − − − − L. innocua 416 − − − − − − − L. innocua 417 − − − − − − − L. innocua 662 − − − − − − − L. innocua 1419 − − − − − − − L. innocua 1425 − − − − − − − L. innocua 1720 − − − − − − − L. innocua 1944 − − − − − − − L. grayi ATCC 19120 − − − − − − − L. grayi ATCC 25400 − − − − − − − L. murrayi ATCC 25401 − − − − − − − L. ivanovii ATCC 19119 − − − − − − − L. ivanovii 3325 − − − − − − − L. seeligeri ATCC 35967 − − − − − − − L. seeligeri 3008 − − − − − − − L. seeligeri 3321 − − − − − − − L. welshimeri ATCC 35897 − − − − − − − L. welshimeri ATCC 43550 ½b − − − − − − − L. welshimeri ATCC 43551 6a − − − − − − − L. welshimeri CCF4 − − − − − − − L. welshimeri 1471 − − − − − − − Aeromonas hydrophila ATCC 35654 − − − − − − − Clostridium perfringens − − − − − − − Enterococcus faecalis ATCC 29212 − − − − − − − Escherichia coli ATCC 25922 − − − − − − − Flavobacterium indolegenes − − − − − − − Klebsiella pneumoniae ATCC 13883 − − − − − − − Proteus vulgaris ATCC 13315 − − − − − − − Pseudomonas aeruginosa ATCC 27853 − − − − − − − Salmonella typhimurium ATCC 14028 − − − − − − − Serratia marcescens ATCC 8100 − − − − − − − Staphylococcus aureus ATCC 25923 − − − − − − − Streptococcus pneumoniae − − − − − − − Streptococcus pyogenes ATCC 19615 − − − − − − − Vibrio cholerae − − − − − − − Yersinia pseudotuberculosis − − − − − − −

[0048] The results indicated that the PCR primers derived from these genes reacted predominantly with virulent strains of L. monocytogenes because the virulence of several of these strains (EGD, 19115, CCF1, HCC7, HCC23 and 15313) was determined previously by mouse virulence assay (Erdenlig et al., 2000). To further verify the virulence of L. monocytogenes strains as determined by PCR, a second mouse virulence trial was recently conducted involving 12 L. monocytogenes strains (Table 4). The validity of PCR determination of the virulence of L. monocytogenes has been again confirmed by the mouse virulence trial. One notable exception is L. monocytogenes strain ATCC153 13, which is avirulent due to a mutation that causes failure to express listeriolysin, a known virulence factor. The PCR results suggest that the other virulence-specific genes in this strain are intact. TABLE 4 Summary of L. monocytogenes mouse virulence trial Mouse virulence Strain Serovar PCR trial LD50 L. monocytogenes ATCC 2 V V   1.6 × 10⁹ 19112 L. monocytogenes ATCC 4a A A   1.9 × 10¹⁰ 19114 L. monocytogenes ATCC 4b V V   6.0 × 10⁸ 9115 L. monocytogenes ATCC 4c V V   2.6 × 10⁸ 19116 L. monocytogenes ATCC 4d V V   8.8 × 10⁸ 19117 L. monocytogenes ATCC 4e V V   7.8 × 10⁹ 19118 L. monocytogenes ATCC 1 V A >1.2 × 10¹¹ 15313 L. monocytogenes EGD ½a V V <1.1 × 10⁷ L. monocytogenes HCC8 1 V V   <7 × 10⁸ L. monocytogenes 4 A A   3.5 × 10¹⁰ HCC25 L. monocytogenes 874 not V V <8.0 × 10⁷ determined L. monocytogenes 1002 not V V   5.2 × 10⁸ determined

[0049] Therefore, the present invention utilizes one or more L. monocytogenes virulence-specific genes that allow detection of virulent strains of L. monocytogenes. Specifically, these genes include lmo0833, lmo2672, lmo1116, and lmo1134 (encoding putative transcriptional regulators); lmo0834, and lmo1188 (encoding proteins with unknown function); and lmo0333, lmo2470, and lmo2821 (encoding proteins similar to internalins). Indeed, the combined use of lmo2470 and lmo1116; or lmo0333 and lmo1116, or the use of lmo2821 alone is sufficient to enable identification of all potentially virulent L. monocytogenes strains under investigation. The scope of this invention also includes other genes identified by the methods described that could indicate virulent forms of L. monocytogenes. For example, the described techniques have been used to identify other genetic markers unique to L. monocytogenes , L. innocua, L. grayi, L. ivanovii, L. seeligeri and L. welshimeri (Table 5), that could be used for the development of species-specific PCR assays. These species-specific PCR assays have been tested against a panel of Listeria and other gram-positive and negative species. TABLE 5 List of bacterial strains examined in PCR using Listeria species-specific primers lmo0733 lin0464 Lgr20-246 Liv22-228 Lse24-315 Lwe7-571 Strain Serovar Source (455 bp) (749 bp) (420 bp) (467 bp) (371 bp) (608 bp) L. monocytogenes ATCC 19111 1 Poultry + − − − − − L. monocytogenes ATCC 19112 2 Human + − − − − − L. monocytogenes ATCC 19113 3 Human + − − − − − L. monocytogenes ATCC 19114 4a Human + − − − − − L. monocytogenes ATCC 19115 4b Human + − − − − − L. monocytogenes ATCC 19116 4c Chicken + − − − − − L. monocytogenes ATCC 19117 4d Sheep + − − − − − L. monocytogenes ATCC 19118 4e Chicken + − − − − − L. monocytogenes ATCC 15313 1 Rabbit + − − − − − L. monocytogenes EGD (NCTC7973) ½a Human + − − − − − L. monocytogenes HCC7 1 Catfish brain + − − − − − L. monocytogenes HCC8 1 Catfish brain + − − − − − L. monocytogenes HCC12 4 Catfish brain + − − − − − L. monocytogenes HCC13 4 Catfish kidney + − − − − − L. monocytogenes HCC16 4 Catfish brain + − − − − − L. monocytogenes HCC17 4 Catfish brain + − − − − − L. monocytogenes HCC18 4 Catfish spleen + − − − − − L. monocytogenes HCC19 4 Catfish spleen + − − − − − L. monocytogenes HCC23 4 Catfish brain + − − − − − L. monocytogenes HCC24 4 Catfish spleen + − − − − − L. monocytogenes HCC25 4 Catfish kidney + − − − − − L. monocytogenes 168 Aborted calf fetus + − − − − − L. monocytogenes 180 Human outbreak + − − − − − L. monocytogenes 418 Freezer study + − − − − − L. monocytogenes 742 Ground beef + − − − − − L. monocytogenes 874 Cow brain + − − − − − L. monocytogenes 1002 Pork sausage + − − − − − L. monocytogenes 1084 Chicken + − − − − − L. monocytogenes 1400 Jalisco outbreak + − − − − − L. innocua ATCC 33090 6a Cow brain − + − − − − L. innocua 415 Turkey burger − + − − − − L. innocua 416 Veal/beef patty − + − − − − L. innocua 417 Beef steak − + − − − − L. innocua 662 Raw milk − + − − − − L. innocua 1419 Ground cheese − + − − − − L. innocua 1425 Pecorino Romano − + − − − − L. innocua 1720 Chicken − + − − − − L. innocua 1944 Ground turkey − + − − − − L. grayi ATCC 19120 Chinchilla faeces − − + − − − L. grayi ATCC 25400 Corn leaves/stalks − − + − − − L. murrayi ATCC 25401 Corn leaves/stalks − − + − − − L. ivanovii ATCC 19119 Sheep − − − + − − L. ivanovii 3325 Cheese − − − + − − L. seeligeri ATCC 35967 Soil − − − − + − L. seeligeri 3008 Soil − − − − + − L. seeligeri 3321 Cheese − − − − + − L. welshimeri ATCC 35897 Plant − − − − − + L. welshimeri ATCC 43550 ½b Soil − − − − − + L. welshimeri ATCC 43551 6a Soil − − − − − + L. welshimeri CCF4 Catfish brain − − − − − + L. welshimeri 1471 Environment − − − − − + Aeromonas hydrophila ATCC 35654 − − − − − − Clostridium perfringens Clinical − − − − − − Enterococcus faecalis ATCC 29212 − − − − − − Escherichia coli ATCC 25922 − − − − − − Flavobacterium indolegenes Clinical − − − − − − Klebsiella pneumoniae ATCC 13883 − − − − − − Proteus vulgaris ATCC 13315 − − − − − − Pseudomonas aeruginosa ATCC − − − − − − 27853 Salmonella typhimurium ATCC − − − − − − 14028 Serratia marcescens ATCC 8100 − − − − − − Staphylococcus aureus ATCC 25923 − − − − − − Streptococcus pneumoniae Clinical − − − − − − Streptococcus pyogenes ATCC − − − − − − 19615 Vibrio cholerae Clinical − − − − − − Yersinia pseudotuberculosis Clinical − − − − − −

[0050] The present invention is also used to detect viable virulent strains of L. monocytogenes. The PCR assay utilized in the present invention is effective in amplifying the above listed gene sequences from chromosomal DNA, which is not effective in distinguishing live L. monocytogenes from dead L. monocytogenes. However, amplification of the above listed gene sequences from mRNA by reverse transcription-PCR (RT-PCR) would only detect the presence of live, viable L. monocytogenes.

[0051] Because transcriptional regulators are essential components in the regulation of RNA synthesis and gene expression within bacteria, and because internalins play vital roles in listerial internalization, they may be potentially useful targets for treatment and control purposes. Therefore, it is also within the scope of this invention to use L. monocytogenes virulence-specific genes (lmo0833, lmo1188, lmo0834, lmo1116, lmo2672, lmo1134, lmo0333, lmo2470, and lmo2821) or their derivatives in the inhibition of growth, reduction of pathogenicity, treatment and prevention of listeriosis caused by virulent strains of Listeria monocytogenes.

[0052] For example, one possible treatment strategy would involve using pharmaceutically active agent(s) that would inactivate or alter the function of one or more of the proteins encoded by the above listed genes, which would either kill the virulent L. monocytogenes or render it susceptible to the host immune system. One possible vaccine strategy would involve altering one or more of the above listed genes or promoter(s) for one or more of the above listed genes such that expression of the encoded protein(s) would be completely disrupted or altered. The said alteration or disruption of expression would render L. monocytogenes avirulent and effective as a live attenuated vaccine.

[0053] While the present invention has been described with reference to specific embodiments and exemplary bacteria species, it will be understood by those skilled in the art that a variety of changes may be made and the substitution of equivalents may be made without departing from the true spirit and scope of the present invention. Many modifications may be made to adapt a particular situation or a particular selected pathogen to the inclusive concept of the present invention. All such modifications or adaptations are intended to be within the scope of the claims appended hereto.

[0054] The complete disclosure of all references cited in this application are fully incorporated herein by reference.

[0055] References

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1 33 1 949 DNA Listeria monocytogenes 1 ataggagacg atttaaatgg ttgcgtatgg tgagttaatt cgcgaagtac ggctttcaaa 60 aggactaacg caaaaagaag tttatacagg agtaatttca aaatcatatg caataggttt 120 tgaaaaagga aaacatgata ttacattagt actatttgaa gaaattttag aacgggtcat 180 gttaagttca gatgaatttt tctttatgaa taggggctat tctttagcgg aggaagataa 240 tttttggtac aaatttgcaa atgcagctaa tcaaaaaagt ttggcagaat tacaagaatt 300 ataccaagaa gtattgcagc aaaatggcga tagagcgaat ctaaggaaag caattgtcca 360 ctcgagaatt gaaattaatg aacaatttct tttgaataat cgatttgacg ttagtatcgt 420 ttctgaggaa gataaagcag ttatccaaac gtatttgtgg aaagttcaat catggacact 480 agaagaaatt cggattttcg ctaattcagt ggactatttt gaagaagatg tacaaattta 540 tttttttcaa ttggtcttga agtcactcga aaaatataag cattacgatc gtggtaaaaa 600 agtattttcc acgctactca ccaacataat agaagaacta atcacccgtg atcaattaga 660 atatgccgcg caattattag aaatactgca cgaactttct tctacgcatg actgtgcttt 720 ttaccggatt atgcataatt actatcaagg cttaatatgg atgaaaaatg acgaggtcga 780 acaaggctta aaagagtcta aaagtgcaat ccgaatttta gatgcacttg attacaaatc 840 cctcgcgcta ctttataata cattacttca acagttttta gaaaaagaga atatacaaat 900 agtttaaagt aaatcagata ccttttataa ggtatctgtt tttttggtc 949 2 1470 DNA Listeria monocytogenes 2 tggagataaa aaaggatgct tactaaaata gctacttatg gttgttgtgc aacaagggat 60 ttgttcaata aagcatttgt tagtgattgg aaaaatcatt ttcaattagt gtcatatcaa 120 cagcattgca gtattgtttc actaatgtca aagccaattg atatcgaact aggagaagaa 180 ctgctgggag agttaagtaa ctttgaaaaa agtgtattta aacaagacgt attaaaatct 240 tttttagaaa ctttaaaaac aactcaacca gaatatttag tgttagattt tcatgtggat 300 acattcaatg gttttattga actcactgat ggggggatta tcactaatcg aatcgtccgc 360 tataagaaat tggatatttt taataaaatg gaagcaagga aagttttttc gccgttagaa 420 aatacgactg agtttagaaa acgttggata cagagtttta accgttttat gcaatttatg 480 aaagaaaatt gccctaatac ccaaattatc attaataggt tagaggttgc acgaatgtat 540 tattctttag ataaccaaat ggaaagcatg atagaacgta gaaaaacaaa agatcaccat 600 actgctgaga cattagctaa aattgatgag tgcatagatt actttgagcg ttatgctatg 660 aataattttg atttacagtc attggacttt aattccgaag aatactttgg tgcagaaaat 720 aatccatggg gaacctgtta tatgcattac aatccctatt attataaaaa aaagtttaaa 780 gatttatgga atatagttga aaatcatttt catgcaccaa caaaattagc tagttttgca 840 cctggaggcc ttgcgaaaca aattccatta ggtgtgacca aattatctga tatggatgaa 900 gtaggagtat attatttaac aaatgctact tacttacaaa tggaggatcg accgacaaca 960 gataatgcag gttatttttt cattgtttat ccgcgaaatg ggaaaaatgg gtatatgcaa 1020 gagctgagaa aatcaacagc agctttttcc attcaaattt ttgtccgaat tactgatgga 1080 aaagagagtt ctaaatggaa catggtaaat agtggctttc gaacacttac aatacctgat 1140 gtgacttcta tttctgaaat tacagaggct ggagaatatt atattactgc agaacaggtt 1200 aagaaacttc aggatcatcc tacaaagaaa aatggttggt ttctaaccgt ttctaagaaa 1260 aatcatgata gcctaaaaca attgttaaca aaaaatactc aaaatgacaa tgcctttgaa 1320 gaatatgttc gacttgtaaa cgtggaaaaa agaacaaact taaaatggcg taaatatcat 1380 tttgatgaag caaacttttc gattatagtt gctatacgta actttaaaaa caaagtggta 1440 cgaagattaa aattaacaaa agcataaaca 1470 3 730 DNA Listeria monocytogenes 3 aggagagatt tttatattaa atcaaaaata tcaattacta cttcataatg aatatgacac 60 aaaaagtggt gatttagtca aaaaagaaat agttgcaact aaaaaaacta aaaatctctt 120 ggaagatcta acttcgcatt tgttatgtgt tacaaatcaa atagagtatg gaaaatttat 180 cacttggtat gaaatggaaa ttaaaaaagt tctacaagtt catcccaatc agcactttat 240 tattaaaatt tcctttcaac aattatattt tcgggaaaca atgctgttgc ttgagaattt 300 acagaaagat agccggcgac taacgattga gctagttgga gatagtcaga ttagccctta 360 ttcaaaggaa catttttccg cagaggacag tgatgctttt ttgaaaggga agttaaaaat 420 gttgaaaaag tggcattatt ttatttcaaa gcatattgaa agtggtgcca tcgaacaaac 480 actgattttt acgccctata ttgatgaatt gaaatatagt ttaacgcaaa agtcgaagct 540 cttacacaat attactgaat taaagttttt tctatcattt tggaaaaatt gggctgagct 600 tcgatttgtt gattttttag ttttagtaga tgaaaaaaac gaatttgtat cgcatgtgct 660 tttaccagat gaattaaatg tacgttgcaa aatgtatgag aactttggag gaatggtcag 720 tgagtaaaaa 730 4 810 DNA Listeria monocytogenes 4 aaaaactgtt ctaaaaagga gggggaacga tgaaaacgaa gatgccggaa atgctttctt 60 tcatttcaga agaagctgtt agtagaaaaa tgacaagtga ggaaattgct gctcactttg 120 gttatgataa acatcacttt agtcgaaaat ttaaagaaat taatggattc agtgtggttg 180 aatttctttc tagtttaaaa gtggaaaagg cgattattga acttgatgaa gaagtacgca 240 tactcgactt acaagaacat tcaggttttg aaagtagtgg tagtttcaca aatacgttta 300 aaaaatatac aggtagttct cctagaaaat acaaaaccga aatgaatgat attttttatg 360 atatgaaacg ttttgaaaat gataataagg ataagtcaat agcgcatttt caagaaaata 420 atgattcttt ttgcaatgta actattgatg tacctgatga atttgagaag ggtatcatat 480 ttattggact tttccgtact cttataccga atcatatgcc tatatcggga ttagctacta 540 aaaatttaat aggaaatcaa ttgaaaaata ttccaagcgg agactattat ttattagctt 600 gtgcgataag ccagtctaat aacattctat cttattttaa cttaagtaat agtttgagag 660 ggaaagaaga tgaaaagcta tcttttccta aatgttctgg caatcattac gcgattaagc 720 tgagaaaacc aataccagaa gatccaccaa tattagctaa tgtgggaaaa attttaatct 780 cctgtttgaa gaacacaatc tagaacaatt 810 5 960 DNA Listeria monocytogenes 5 aaacaaattc attaatcatt ttaagcacct ccatatcatt agtttaacaa agcatttacg 60 tttttcattg tatatttgcg acattttgca gaaaaatttg cttcatttct tctggggtat 120 gattactata tcgtttaaat tgtttaatta agtgagcctg gtccgtaaac ccatgaagat 180 aagcaagttc agcgcccggc acacttggat tctcatataa tgcctgtaat actttttgga 240 aacgaataag ttttgctgtc tgtttaggtg caagtcccat gtgtttttga aacagccgtt 300 ctaactgccg aacagataca gctcctaaca caaattgatt ggggttttgt agtaacttat 360 caatactgtt taaaaaatca ggatggactt gcttgccaag catcattaat tttcgcagta 420 aaaattcttc taataaagct attctttcac tgttcgtcgt catttcagca aacctctctt 480 gaaaaaacga aacaaatcca gcaaacatct cttccggctc ttttacccga ttcatgctac 540 cagtcaagtc ctgttcgaca aataaaaata acgaccacgc ataaaatcgc acggcaaaaa 600 gctcggtatt actttcatcg tcagactcaa acgatgcatc actaacgcca acaaatatag 660 catccgtcac tagccctgtt ttactatcaa ttgtaaaaat aatatccgca cataaatcag 720 gaaccactaa attatttccc gggaaattct tatcatctgc ctcccaaaaa cagcgaatat 780 agcctgtaag agctgcactc ggtagatatt ctttatagcc agcacgcttt ggtgtagcta 840 caatgggata aaacgtttct agcttagcca taaagagacc cccttttcct catagtacca 900 caaaattttc tctttaatca tgcttctttc ttttatttat gggtattaag taaataaggg 960 6 390 DNA Listeria monocytogenes 6 ggagtacacc cgatagcaag gaggaactag atgtatatta aagattttgc cactaaaacg 60 gggctttcga ttgatacgct tcgatattat gaggaagaaa aattattaat acctgctaga 120 aatgaaaaaa attatcgtgt ttatacggaa gaagattact gctgggtaca gcttttactt 180 aaaatgaagc aaacagagat gacaataaca aacattaaaa attttgctac attacaaaag 240 caaggagata aaacactccc aaatcggata caaattttag ataatcatat ggaaaacttg 300 tatgaacaac agaaagattt agcagaaacg atttcttttg tggctaaaaa agtggatggg 360 tatcgagaga agttataaaa acaacaggaa 390 7 4470 DNA Listeria monocytogenes 7 aagtcttgaa aaagaaattt agtatagtta ttatcagtgt attgttactt ggttatttag 60 cgccttttga tactttgtta gtaggtgcag atgaaacaac ggtttctgaa gatacagcag 120 ttaaaacggc agaagcagat agtgctactg aaggcataga aagcgaaaca ggttcagatg 180 atgaaacggc agaagagcca aaagaagcaa aagaggcaga agcaagcaaa gaaacgacag 240 aaaaagagga aaaagcgaaa acggaagaac cggcttctaa tattaaaacg gagattaata 300 cagataaaag ccagctgaaa caaactagct taaaagcagc ggtgccagca ggaagtacat 360 ataattcttt gtttccagac gacaatcttg ctaaaaaatt agctgtgatt atcacaggaa 420 atgcggctgc aacaggtaat gaatcagtgg atagtgcagc tcttttagca ataagccaac 480 ttgatttgag tggggaaacg ggcaatgacc caacggatat ttccaatatt gaaggattac 540 aatatttaga gaatttaaca agcctgaatt taagtgagaa taatatatcc gacttggctc 600 cacttaaaga tttggtaaac ctggtttcac ttaacctttc ttccaatcga acattagtaa 660 atctttcagg ggtggaggat ttagttaatt tgcaagaact taatgtctct gcaaataagg 720 cgttagaaga tatttcacaa gttgcatcgt tgccagtgtt aaaagaaatt agcgcgcaag 780 gctgtaatat taaaaccttg gaattaaaga atccggctgg tgctgttttg ccagaactag 840 aaacatttta tttgcaagaa aatgatttaa ccaacttaac ttcattagcg aaacttccaa 900 aattaaaaaa tctctatatt aaagggaatg cttctttaaa aagtttagag acattgaacg 960 gggcgacgaa gctccaattg attgatgcga gtaactgtac cgatttagaa acgcttggag 1020 atattagcgg gctttcggaa ctcgaaatga ttcaattaag tggttgtagt aaactgaaag 1080 aaatcacaag cttgaagaac ttgcctaatc tggtgaatat tacggcggat agctgtgcaa 1140 ttgaagattt aggaacactg aataatttac caaaattaca gacattagtt ctttcagaca 1200 atgaaaattt aaccaatatt actgcaatta ccgatttacc acaattaaaa acattaactt 1260 tggatggctg tggaattaca tctattggaa cgcttgataa ccttcctaaa ttagaaaaat 1320 tagatcttaa ggaaaatcaa ataactagta taagtgaaat aaccgactta ccgcgattaa 1380 gctatttaga tgtaagtgta aataatctta caaccatagg ggacttgaaa aaattacctc 1440 tattagaatg gctgaatgtt agttcgaata gattatcaga tgtgagtaca ctaacaaatt 1500 tcccgagttt aaattatatt aatatatcaa ataatgtcat tagaacagtc ggtaaaatga 1560 ctgaattacc ttcgcttaag gaattttacg ctcaaaataa cagtatatca gatatttcga 1620 tgattcacga tatgccgaat ttaagaaaag tggatgcgag taacaaccta attacaaata 1680 taggtacctt tgataattta ccaaaattgc aaagtctaga tgtgcattca aatagaatta 1740 caagtacatc agttatacat gatttaccaa gcttggagac gtttaatgcg caaactaatt 1800 tgattaccaa tattggtacg atggataatt taccagattt aacctacgta aacttatctt 1860 tcaacagaat accgtcgctt gctccaattg gtgacctacc caatttagaa acattaatag 1920 tatcagataa taattcttat ttaagaagcc taggaacgat ggacggtgtt cctaaactga 1980 gaattttaga tttacaaaac aattacctta attacactgg aacagaagga aacctaagtt 2040 cattaagtga tttaacaaat ctaacggaat taaatttgcg aaataatgtt tatattgatg 2100 atataagtgg actttccacg ctatcaagac tgatctactt gaatttagat tccaataaaa 2160 ttgaagatat ttctgcattg tctaatttaa cgaatcttca agagttaaca cttgaaaaca 2220 acaagattga aaacatttca gcacttagtg atttggaaaa tttaaacaag ctagttgtat 2280 caaaaaataa aattattgat attagtcctg tcgctaatat ggttaatcga ggggcaattg 2340 taactgcgag taatcaaaca tatacattgc caactgtatt atcatatcaa agctcgttta 2400 ccatagataa tccggttatt tggtatgacg gcacactact agcgccatca tccataggaa 2460 actctggtaa ttacaaggac gggaaaataa cttggactaa tatgaccgct acgtctagtt 2520 ccactttatt taactttaat aggttaaaag acggtttaac cttctcagga acagtcaccc 2580 aaccttataa atctgcagcc aaagtaactg cagatgcaga gcaaacttat acaattggtg 2640 atactatttc agaggagcag tttttaaaag atgttaatgc aaaatcatca gacggggcac 2700 ctgttacaag tgattttgct acagtggtgg atttaaacac ttttggcgaa tatgaagtta 2760 ctttaacttc cgaaaaagat ggaatccaag gggatagttg caaagtaatt gtcaaagttc 2820 ttcacggagc gcctgtcatt tcggcagacc aaacaattag ttatgataaa catgcaacta 2880 ttacagagaa acaattttta gaagatattc atgccagcac agacttggat acagctatta 2940 caaccaattt tagtacagca gttaacttga ataaaggcgg agattataca gttgcactaa 3000 actctgaaaa tgaggacggc gtgaaagctg aaacggttta tgtcactgtt actgtaaata 3060 aagacccagc gccgattata agtgctaaga cagaaatcac gtatgataaa ttctcgaaaa 3120 aaaccgaagc ggcgttctta gatgatatag acgcagatac aaatgatggc tctatagtaa 3180 cttctaattt tgctacagca gttaatttag ataaagctgg tgattatact gttacactga 3240 attctattaa tagtgatggt gtagcgggca cgccaacagc gattattgtg catgtggaga 3300 aagagaaaat agcaacaatt agcacaaata cggcacaaca atatgaaaaa tatgcgaaga 3360 ttaatgaaac gcaatttcta aaagatgttc atgctagtat taacgcgagc ccaacaaccg 3420 cagttttgga aagtgatttt gaaacagtag ttaaactaga cgtcccagga acgtacacag 3480 taacgattac tgctacaaat gaagatggcg gagtatcggc acctaaagaa gtttctgtca 3540 tagtaaggaa aattccagca ccagagatca ctgcagataa ggaaataact tatccgaaat 3600 ttgatgaagt aagtgaagca gaatttttaa atgatattca tgcaactatt agtgacaaaa 3660 atgtagcgat tacaagtaac ttcagcacag atgtgaattt aaataaagct ggcgattaca 3720 cagtaacatt aaatgctacg aatgaagacg gcgtaaaggc tacaccggtt gaagtaattg 3780 tacatgttca acaaggagaa cgccctgtta taacagccga tgcaactatt tcctatgaca 3840 agttcgctaa cataacggaa gcgaagttct tagaagatat tcatgcaaca agtagtgatg 3900 gtcaaagctc tactgtaatc acctctaatt tccagaccgc gacaaacttc aaaacagcca 3960 tgagctacac agttacgctt aatgctgtaa atgaagacgg cattagcgca gaaccagtag 4020 cagtgaccgt tacaataaat aaagaaccag ccgcggcgtt aaaagctgat gcagaagtaa 4080 gctatgcgaa aaatgaagct gtaaccgaat ccgatttctt caaagatgtt catttagaag 4140 gaacggaagc gccaagtaca gccaaagcaa caagtaattt tgattccgta gtagatagaa 4200 gtaaaacagg agattatact gttacgataa atgctacaaa cgaagatggg gctgtttcta 4260 caccaattga agtaattgtt catattgaag cagaaagtgc accagtaatt acagcgaatg 4320 cagaagtaaa atataacaaa catgaacaaa cagacgaaag aagattttta tatgatagtg 4380 aagcaaaaat cgatgaagct aatgtggaaa ttaaaaccga ttttgcagaa aaagtagata 4440 ttaataaagt tggaacttat actgtcacac 4470 8 1190 DNA Listeria monocytogenes 8 gaaaggactg aatacattga gaaaagtttt aatgttttta agcacagctt tattattagc 60 cattctgtca ctaagcttta ctggtttaga tctgaaggca aaagctgctt ctgatttata 120 tccactacct gctccaatta ttgatgtttt cccagatgat ggattagcca aagatatggc 180 taaaaactta aacaaagact ctgtgaatga tgttattgac caagatgact tggatgcatt 240 aactggtttg ggatttgaaa caagtacgat tacgaatgat tccatgcaat tactagaacg 300 tgccatgttt aacaatgtca cagatgtaag tattatggaa tttggggcta aactaacgga 360 gttccctgat attacaacca tcccacattt aaaaacgtta ttttttgctg atccacctgg 420 aagattaact agaaacttgt cccttccaaa ctaccaaaat tatcctgaaa tggataccat 480 tacaatgagc ggaaataatt taatcggttc tatccctgat ttcactggaa tgcctgcttt 540 aaaacagctg tatatgtctg aaatgttaat tacaagcgat gaacttccta attttaataa 600 tattccttta cttattacgt tggatctaag ttctaaccaa ttgacaacta ttcctgattt 660 tcaaaatata ccaaatctca catttttaga tttaaatgca aatttattaa ccaatacacc 720 tgattttcaa aatttaccta aattaactga tttaaattta agacataaca atttaactgg 780 tacgatggtt aactacacca acttacctag tttagaatcc ttaaacttag attacaattt 840 tttaactgaa ctaccgtcta atgtattaga taccatctat gttcaaagtc aaaacggaga 900 gcttcctgat caaactatta atcagggcga tacctgtact attgatttac ctatttattt 960 ccaaatggaa gaaactaata tgttagtcag cccagaagtt acgggagaat atatcgggat 1020 tagtgtaatc cagcttccga cgacggttaa tgaggaaggc aacaccataa cagtggatac 1080 atccgctcta agtcctggtg agtataaatt agatgtctcg tataatcaca attatgctac 1140 tggaggcgta tgctcttatg attggaatgt aactattaat taatttctac 1190 9 2640 DNA Listeria monocytogenes 9 taaaacggcg tataataaat gattatagag aacgaataag gagtgcgcca aattgaaaac 60 tactaaaata gtaattgcct cattagttag tttaaccatg gtttcaaacc cgcttttaac 120 attcgcagca acgaatgatg ttattgataa tacgacagaa atcactactg ataaagaaac 180 aagctcaact caaccaacta taaaaaacac actcaaagcc ggtcaaacac aaagttttaa 240 cgactggttt cctgatgaca attttgcttc agaggtagca gcagcatttg aaatgcaagc 300 aactgacact atcagcgaag aacaactagc tactctaaca agtctagatt gccataattc 360 atccataacc gatatgactg gtattgaaaa attaactggt ttaacaaaat taatttgcac 420 aagtaacaac attaccaccc ttgatcttag ccaaaacact aatttaactt atctggcatg 480 tgattcaaat aaacttacaa accttgacgt aaccccgctt acaaaattaa cctacttaaa 540 ttgcgacacg aacaaactca caaagttaga tgtaagtcaa aatccactgt taacttattt 600 aaactgcgcg cgcaacacct taaccgaaat agatgtcagc cacaatacac aattaaccga 660 gctagactgc catttaaata aaaaaatcac caaattagat gtgacaccac aaactcaatt 720 aacaacctta gactgtagct ttaataaaat aactgaatta gatgtaagtc aaaataaact 780 actgaaccgt ctaaactgcg acactaataa tataactaaa ctggacctca accaaaatat 840 tcagctaact ttcctagatt gctccagtaa caaattaacc gaaatagatg taaccccgct 900 tacacagtta acatattttg attgtagcgt aaatccttta actgaattag atgtatctac 960 gctttcaaaa ttaactacac tacattgtat acaaacagat ttattagaaa tagacctaac 1020 acacaacaca caattaatat attttcaagc tgaaggatgt agaaaaataa aagagcttga 1080 tgtcacgcat aatacacaat tatatttatt agactgccaa gccgctggta taacagaatt 1140 ggatctttca caaaacccta aattagtcta tttgtattta aataatactg aactaacgga 1200 attagacgtt tcccataaca caaagctgaa aagtttgtct tgcgtaaatg cgcacatcca 1260 agacttctct tctgtaggta aaattcctgc ccttaacaat aattttgagg ctgaagggca 1320 aacaatcacg atgcctaaag aaactttaac aaacaacagc ttgaccattg cagttagccc 1380 tgatttatta gatcagtttg gaaatccgat gaatattgaa ccgggagacg gcggtgtgta 1440 cgaccaagca acaaatacaa taacttggga aaatctcagc acagacaatc cagccgtaac 1500 ctatactttc acttccgaaa acggagctat agtaggaacc gtaacaactc catttgaagc 1560 acctcaaccc atcaaaggag aagacgtcac agtacattac cttgatgaca aaggagaaaa 1620 attggcggat gatgaagttc taagcggtaa tttggacgat ccttatactt ctagcgcaaa 1680 agacatccca gattatacat taacgactac tccagataac gcaaccggaa cattcaccac 1740 tactagccag tccgtaacgt acgtttacac taaaaacatc gtagccgcag agcctgtaac 1800 cgttaattac gtggacgata ctggaaaaac gctctctcca tccgaaatat taaacggaaa 1860 tgttggcgac acttataacg ccactgccaa acaaatcgac ggctacacat tatccgccga 1920 accaaccaat gcaactggac aattcacaag cagcgcgcaa accgtcaact atatttacac 1980 aaaaaatcca gcccctgaaa aaggagttgt agaaattcac tatgttgacg aagataataa 2040 acaacttaac tccaccacag aaatttctgg aacaatagga gataactaca cgactgagcc 2100 aaaaactatc gaaggctata cgttaacaac tacaccgggt aatgcaaccg gcactttcac 2160 cacaggcagc caaaccgtga catatgtgta tactaaaaac atcgaagcag cagagccgat 2220 aacagtgaat tacgtggatg ctaatggcaa aacactcgct ccatccgaaa cattaaacgg 2280 aaacgttggc gacacatata aagcaactgc caaacaaatc gacggctaca cattatccgc 2340 cgaaccaacc aatgcgactg gacaattcac aagtagcgca caaactgtca actacattta 2400 tacgaaaaac acaaacacag atcaaccttt accaactaaa aaacctacga acaccacacc 2460 aaccaagcca tctaatttaa agacaaccga agtgaaaaaa gcttcagata ccctaccaaa 2520 aacaggcgat tccgcaccat ggaaatcagc tctacttggg gtattcctat catccacagc 2580 tctagttatc tggaaaaaga aaaaatagta aaaaagccgg acaggattaa tttcccgacc 2640 10 20 DNA Artificial Sequence primer 10 ggctattctt tagcggagga 20 11 20 DNA Artificial Sequence primer 11 agtagcgcga gggatttgta 20 12 21 DNA Artificial Sequence primer 12 tttcgccgtt agaaaatacg a 21 13 21 DNA Artificial Sequence primer 13 ttcggacaaa aatttgaatg g 21 14 24 DNA Artificial Sequence primer 14 aacttcgcat ttgttatgtg ttac 24 15 20 DNA Artificial Sequence primer 15 tcactgacca ttcctccaaa 20 16 20 DNA Artificial Sequence primer 16 gggaacgatg aaaacgaaga 20 17 21 DNA Artificial Sequence primer 17 tggcttatcg cacaagctaa t 21 18 20 DNA Artificial Sequence primer 18 cggcacactt ggattctcat 20 19 20 DNA Artificial Sequence primer 19 agggctagtg acggatgcta 20 20 20 DNA Artificial Sequence primer 20 acccgatagc aaggaggaac 20 21 22 DNA Artificial Sequence primer 21 aacttctctc gatacccatc ca 22 22 20 DNA Artificial Sequence primer 22 ccgatttaga aacgcttgga 20 23 20 DNA Artificial Sequence primer 23 ttcggcatat cgtgaatcat 20 24 24 DNA Artificial Sequence primer 24 tgattccatg caattactag aacg 24 25 26 DNA Artificial Sequence primer 25 aggattctaa actaggtaag ttggtg 26 26 21 DNA Artificial Sequence primer 26 tgtaaccccg cttacacagt t 21 27 20 DNA Artificial Sequence primer 27 ttacggctgg attgtctgtg 20 28 540 DNA Listeria monocytogenes 28 aaaggcggtt atctctaatg ttaaacgaaa atattaaagc aatcagaaaa tcaaaaggac 60 tttcgcaaga agaaattgcc atcaaactga atgtggtgcg acaaacaatc tctaaatggg 120 agcaaggact gtcagttcct gattccgata tgttaatctc catatcggaa gtgcttgaaa 180 caccagtaag cactttgctt ggagaaactg ttatggtttc aaaggttgat gatgtaaaag 240 caatttccga aaaactggag attataaact tacagtttgc tcaaagaaag accgccagac 300 gaaaaatgct ttattggcta tttgtctcgt tgtgtgccgt tatagcaata atttctgcgg 360 tctttataat actaaatagt ccttacttag gttgggatta tagtgatcct gaaactagcg 420 ttatcggagt agcttttcat acatttgaat ggttgtttgt cagattagca ccgattatcc 480 ttataggagg agtcgttgga atttttctaa cgcggaagaa cgtataaaat cgtactatgt 540 29 1080 DNA Listeria monocytogenes 29 aaagcattac aagattttct taaataaata aagcaaaaca cggaaatcca ttcttcggat 60 ttccgtgttt ttttagatga aaaaaagcat taactttcgt aaattgagac tatatcataa 120 attctacgct tcattttttc acgaacatgt aatggctcta aacattcgca tttatcgcca 180 aaactcaaga gaatatcata gtgatactcg ttttctataa aaggaaaact gacaatgtaa 240 tgctcctcac catcgggata aaaattttca taagagcaat aatcaagcac tctatcgata 300 atggattgat gaatacgaat tttaatttct atctgcataa ttgctacaat atcttccatt 360 tctaactgtg gcttttgaaa atctcgcagt gtaaaagtgt cctcaagtat ttgcagacca 420 gacatacgag ataacctgaa taaacgaaaa tcattcctat tttggcaata cccatacaaa 480 taccagtggc tgcttttcat tacaagctga tatggttcaa ctattcttac ggtcttattt 540 ccttggtgag ctatatattc aaaggttagt aacttgtttt cctgcaaagc cactttgata 600 atttctacat gtggttgtat gttgttattt cccgtccact ggcttaaatc tatataaatt 660 tggttcgctt ttagctcgat ttcttttgct ctatcagctg ggataaaact ttttattttt 720 gcaagagcat ttatcagttc atctccgcgt accatgttag aaagacttga aaggcccata 780 agaatagcgg aaaggtctgc tgttgaaaaa accttgctat ccatcttgta gtcaggcata 840 atttcaaacc cgccacctac gcccggtgtt gaacgaatag gtacaccagc caagtcaatc 900 gcgtctatgt cacgataaat tgtacgaagc gaaacttcaa atctatcagc taactcttgt 960 gcgctaatac gttctttatc aaggagaatt aaaacaatgc tcataagcct atcaactttc 1020 atataatagc cacctttcaa aattactata tattgttgcc ataatggtgt caacaatcgg 1080 30 772 DNA Listeria monocytogenes 30 gatctgcatt gtaaacgcca tccacattgt tcttcgccat taaaatcacg tctgcttcaa 60 tttctgctgc ccgaagcagc tgcagttgta tctgtcgaga aatatggatt tcccgtacca 120 ccagcgaaga ttacgacacg tcctttttcc aagtgtctga ttgctttccg gcgaatataa 180 ggttcagcga tttggcgcat atcgatagaa gtttgtacac gtgttgctac cccaatattt 240 tccaaggaat cttgaagaga taaggaattc atgaccgttg caagcattcc catataatct 300 gctgctgcac gatcaaggtc aatcttaccg gtcagttctt aggtcttaaa tatgtgctac 360 ctattttaac gaaacaagga aatggaagcg ttatcaacac ggcttctgtg gccggacttg 420 atggcagttc ctttttagcg ccatatgtgg cttcaaaaca cggcgtcagt ggtctgacaa 480 aagtccgcag cactagaagt agcggataaa ggtgttcggg tcaactccgt ccatccatca 540 ccagtcaata cccggatgat gcgatcgatc gaaaagaatc tcaacccaga cgatgcggaa 600 aaagcaaaag aagaatttac aaaagatatt ccagtcggaa gatatgcaga agccagcgat 660 gtcgcgaaac ttgtcttatt cctagcctcg gacgatagca aatttatcac tggtgcgcaa 720 tacgggtaga tggcggtatg ggggctacac aataaaatta aaaataaaga tc 772 31 1377 DNA Listeria monocytogenes 31 gatcttgtag ccgatataat aatctcgtaa tttgttgttc attaagcata tttatagaac 60 ctcccataat gaatgcgctg gcatacagat tattatagca tggcttcatt tgtttatcac 120 gaattcctta ttcacttgag ctatttattc tagtcttttt ttagaacatt tttactttct 180 atagagaaaa ttactacttc aaggcttatt actaagcaat aattaattta ctaaaaatgg 240 ctttatacca atattcacct gtttttccgt tttttaaaaa caactttcac taaaaacaac 300 ttcacaattt ttacacattt aaccaactaa gtaaaaatcg ctatatatca gtcatttaac 360 caatttttaa tttttcgtta tacaattgta atagattttt tttcttgttt tttgatatta 420 taattacaaa tagataaaaa aggagtgctt agaactgtgg ataaaaagtt tatgaaatca 480 gggattatta tactcattgt ggcatttatt gtagtttcaa tgaatgttgg agcagaaacg 540 ggtgataatc aggtttctca agttgagtta agttcgcagc aacaagcatt tattaatgaa 600 attttacccg ctgctcaaga tggtctacgt gacggaaagc ttttagccag tgtaacactc 660 gctcaagcta tattggaatc taattggggt gaaagtggtt taagcaaaaa ctcgaataat 720 ttatttggta ttaaaggttc gtataatggg aaatcagttt cgatgcgtac gatggaagca 780 actggggcaa caactgcgaa tttccgtgtt tatcctagct ggcaagaatc cattaaagac 840 catactgatt taattacaca caacgcacgc tataaaggcg cagtcggcga aacagattac 900 cgcaaagcta tacaagcaat taaagatggt ggttatgcga ctgatcatgg tgcagaaaca 960 gtagaagtta gacgcaaaaa tggtaagaac gaaacggcaa ccattaattt gaaagccttt 1020 catagtggta ataatgttgt tatcgaaatt gtagatgatg gtgctggtat taacaagcga 1080 aaagttttag agaaagcgat tacgaaaaac gtagtaacga gagcagaatc taccaaaatg 1140 acggatagcg aaatttttga tttgctgttt gactcaggat ttagtaccgc tgatctaaag 1200 cttttcggct ccctaaaaac tatccgtgcg gaaaaagact ataaaaaagg attacaagtg 1260 cttgataaaa acttttacgg caccatttcc gactttgatt tagaatagaa gtggccgatt 1320 atgtcaaagg taaagaaatt ttcactaaat tattaaaaga ttatcaaata acagatc 1377 32 1537 DNA Listeria monocytogenes 32 gatcatttat cgtatcaaca tcccgttaga ttttcatttc cggaaaggat taatgtttcg 60 taatttcggt agattttcta atgtccccaa atcttctatt atcgcaatta ttgcagtaat 120 attagttaaa ttaggtagat tttttaaatc tgtaatttct tttaacttac tacaaccact 180 tagttgaatc atttcaaggg tatgtaatcc cactaatgtc tccaactgtc tccatatccg 240 tacagttact cgcatcaatt aattggattg aggtagaacc atttaatgtt tctaaacttt 300 ccaaagaaga atttcctttg atataaagat ttttcaattt tggtaatgtt gctaatgcag 360 ttaaatcttg caagtcattc tcttgtaaat aaaatgtctc tagttcaggc aaagcatcct 420 cccgcaggat ttttcaagtt ctaatgtttg aatgtttaca acccttgcgc actgatttct 480 ttcaaggctg gtaacggctg ctactggtga aatatcagct aaagattcta ccaagttgat 540 acatttaaaa tcctgtaaac tggggtaaac cttcccacac ccgtttaaag tcttctaaaa 600 ttttggtctg gaagaagaga tttattagcc accttatttt ccgttaaacc agtcaagtcg 660 gtgagacatc agttagggtg aatttctcac taaaatttaa cctccgttta ccgtattcta 720 aaatactaga aaccccctta attactcccc aaactcaaat gtctttgcac caagcccgtt 780 tcccgctaaa ttagtgggga ggaaaaagtc ccgcgatttt ggtaatttat cacaatggga 840 gggcttccca ggaggaaaaa gcaatttttt gccaagattt tcatctgtaa caaagaatta 900 tatgtactcc cagcaagaac atctgttttt aatttagatt gctttgaagt tggttttctg 960 tttttggttc taatttagga gtgacggctt acttctttcg gatctgtagg tttttccgcc 1020 tcttgttcta atggttcttc tttaacttct gtaatctgaa ttagtttcaa taaccggtgt 1080 tttttcttca gttatttctg attttgtcgt taaatcttca ggaacagttg tttcttccgc 1140 gacggctaaa gtactaaatg gagccaaata ccccaacaaa agagcactaa caattaccat 1200 actaagtttt ttcttcaaga ctttccctca tttcgttcaa attaatttaa cattttttgg 1260 tgctccattt attatacatg gcttgaatac gccatttgtc tttttaaaat acttatcaaa 1320 acagaaatat gtagatttta tgtcgccaga aaaactagtt tttttaaaac gagctagaat 1380 gttgctctaa tgctattttc actcaaaaaa aacaagccag ataatttcgg cttgtttcga 1440 tgtttatatt attcattttt atttttcgat aactactgga ttttgtacat gtacgacttc 1500 aaagcgagca atttcattgc cgacaattcc tttacga 1537 33 825 DNA Listeria monocytogenes misc_feature 610 n = A,T,C or G 33 cattggtgtc cttttagctg tgtggttaat gtgtgtgctc gagaaaaact tgcgtaaaat 60 aattccgaat gcgatagata tcattttcac tcccacattg gtgctactca ttattggtgt 120 agtaactatt ttcttaatca tgccattcgc cggacttgtt tctgatggat tagtgaacgg 180 aatcaactgg gttatcgaag ttggcggtgt ttttgccgga tttgttcttg gtacattatt 240 cttaccaatg gtcatgtttg gtttacatca agttttaaca ccaattcatg tagaaatgat 300 tgcccaaagt ggttatacaa tattattacc gattttagca atggcaggtg gtggacaagt 360 cggtgcatcc atcgctcttt ggattcgttg tcgtaaaaat aaaccacttg ttaacatgat 420 taaaggtggc cttccagtag gtattttagg aattggcgag ccattaattt atggagttac 480 cattccactt ggtagaccct ttctaactgc ttgtcttggt ggtggtattg ggggcgcagt 540 gattggattc ttcggaaaca ttggttcgat tgccattgga ccttctgggg tagcgcttat 600 tccattaatn cgctaacaat gaatggttgg gatatatcat tggtctagta gctgcatatc 660 taggcggatt tatcttaacg tattctttgt acgccaaaag atgcgatgca aatgtggaat 720 ataaactaag ttgactaatc aaagccatta aatgatttat tatttaatgc cctttactat 780 ttacaataag caatttaaat gtaaaatcaa agaaagagtt ttgac 825 

What is claimed is:
 1. An isolated virulent gene of L. monocytogenes.
 2. The isolated gene of claim 1, wherein said gene encodes a protein having virulent biological activity.
 3. The isolated gene of claim 1, wherein said gene comprises a nucleic acid molecule selected from the group consisting of SEQ ID NOS.: 1-9.
 4. The isolated gene of claim 3, wherein said gene encodes a protein having virulent biological activity.
 5. The isolated gene of claim 1, wherein said gene comprises a nucleic acid molecule having 95% sequence homology to a nucleic acid molecule selected from the group consisting of SEQ ID NOS.: 1-9.
 6. The isolated gene of claim 1, wherein said gene comprises a nucleic acid molecule having 90% sequence homology to a nucleic acid molecule selected from the group consisting of SEQ ID NOS.: 1-9.
 7. The isolated gene of claim 1, wherein said gene comprises a nucleic acid molecule having 80% sequence homology to a nucleic acid molecule selected from the group consisting of SEQ ID NOS.: 1-9.
 8. The isolated gene of claim 1, wherein said gene comprises a nucleic acid molecule that binds to a specific primer or probe, said primer or probe being selected from the group consisting of SEQ ID NOS.: 10-27.
 9. The isolated gene of claim 1, wherein said gene comprises a nucleic acid molecule that binds to a polynucleotide fragment having 95% sequence homology to a primer or probe selected from the group consisting of SEQ ID NOS.: 10-27.
 10. The isolated gene of claim 1, wherein said gene comprises a nucleic acid molecule that binds to a polynucleotide fragment having 90% sequence homology to a primer or probe selected from the group consisting of SEQ ID NOS.: 10-27.
 11. The isolated gene of claim 1, wherein said gene comprises a nucleic acid molecule that binds to a polynucleotide fragment having 80% sequence homology to a primer or probe selected from the group consisting of SEQ ID NOS.: 10-27.
 12. The isolated gene of claim 1, wherein said gene comprises a nucleic acid selected from the group consisting of SEQ ID NOS.: 1-9.
 13. A novel primer or probe for the identification of virulent genes of L. monocytogenes, said primer or probe being a polynucleotide fragment of at least 10 base pairs that bind to or are complementary with a portion of at least one polynucleotide selected from the group consisting of SEQ I) NOS.: 1-9.
 14. A novel primer or probe for the identification of virulent genes of L. monocytogenes, said primer or probe being selected from the group consisting of SEQ ID NOS.: 10-27.
 15. A method of identifying virulent a L. monocytogenes isolate comprising: providing at least one primer or probe specific for a corresponding at least one virulence-specific gene of L. monocytogenes; conducting PCR assay or hybridization using said at least one primer or probe to identify the presence of said corresponding at least one virulence-specific gene in said L. monocytogenes isolate.
 16. The method of claim 15, wherein said virulence-specific gene is selected from the group consisting of genes identified by SEQ ID NOS.: 1-9.
 17. The method of claim 15, wherein said at least one primer is selected from the group consisting of SEQ ID NOS.: 10-27.
 18. The method of claim 15, wherein said at least one primer or probe is two or more primers or probes and said corresponding at least one virulence-specific gene is two or more virulence-specific genes and said PCR assay or hybridization is multiplex polymerase chain reaction or hybridization.
 19. The method of claim 15, wherein said PCR assay or hybridization is multiplex polymerase chain reaction or hybridization using said primers or probes specific for said virulence-specific gene in combination with Listeria genus-specific primers or probes or L. moncytogenes species-specific gene sequence.
 20. The method of claim 15, wherein said L. monocytogenes species-specific gene sequence is selected from the from the group consisting of genes identified by SEQ ID NOS.: 28-33.
 21. The method of claim 15, wherein said PCR assay or hybridization is multiplex polymerase chain reaction or hybridization using said primers or probes specific for said virulence-specific gene in combination with Listeria genus-specific primers or probes and L. moncytogenes species-specific gene sequence.
 22. The method of claim 17, wherein said L. monocytogenes species-specific gene sequence is selected from the from the group consisting of genes identified by SEQ ID NOS.: 28-33.
 23. The method of claim 15, wherein said at least one virulence-specific gene is involved in inhibition of growth.
 24. The method of claim 15, wherein said at least one virulence-specific gene is involved in reduction of pathogenicty.
 25. The method of claim 15, wherein said at least one virulence-specific gene is involved in treatment of pathogenicity.
 26. The method of claim 15, wherein said at least one virulence-specific gene is involved in the prevention of virulent strains of L. monocytogenes.
 27. The method of claim 15, wherein said at least one virulence-specific gene is detected by amplification of said genes from mRNA and said PCR is reverse transcriptase-PCR (RT-PCR).
 28. A method of identifying viable virulent strains of L. monocytogenes comprising: providing at least one primer specific for a corresponding at least one virulence-specific gene of L. monocytogenes; using said at least one primer to identify said at least one gene and amplifying sequence of said gene from from mRNA by reverse transcription-PCR (RT-PCR).
 29. The method of claim 28, wherein said virulence-specific gene is selected from the group consisting of SEQ ID NOS.: 1-9.
 30. A method of treating a host subject in need of treatment for the pathogenic effects of a virulent strain of L. monocytogenes comprising: administering an effective amount of at least one pharmaceutically active agent that is effective in altering or inactivating the function of at least one protein encoded by a virulence-specific gene.
 31. The method of claim 30, wherein said virulence-specific gene is selected from the group consisting of SEQ ID NOS.: 1-9.
 32. The method of claim 30, wherein said altering or inactivating kills said said virulent strain of L. monocytogenes.
 33. The method of claim 30, wherein said altering or inactivating renders said virulent strain of L. monocytogenes susceptible to the immune system of said host subject.
 34. A vaccine to protect a subject from the pathogenic effects of a virulent strain of L. monocytogenes comprising: altering said at least one virulence-specific gene so as to render expression of the encoded protein of said at least one gene ineffective, wherein said resulting L. monocytogenes is rendered avirulent and effective as a live attenuated bacteria suitable for use in a vaccine for said virulent strain of L. monocytogenes.
 35. The method of claim 34, wherein said virulence-specific gene is selected from the group consisting of SEQ ID NOS.: 1-9.
 36. A method of vaccinating a subject to protect the subject from the pathogenic effects of a virulent strain of L. monocytogenes comprising: administering a purified protein encoded by a virulence-specific gene or administering a live viral or bacterial vaccine expressing a protein encoded by a virulence-specific gene or administering a DNA vaccine comprising a virulence-specific gene.
 37. The method of claim 36, wherein said virulence-specific gene is selected from the group consisting of SEQ ID NOS.: 1-9.
 38. A method of quickly determining if a sample taken from a food product contains a virulent strain of L. monocytogenes, the method comprising: isolating L. monocytogenes from said food sample; providing at least one primer specific for a corresponding at least one virulence-specific gene of L. monocytogenes; conducting PCR assay using said at least one primer to identify the presence of said corresponding at least one virulence-specific gene in said L. monocytogenes isolate.
 39. The method of claim 38, wherein said virulence-specific gene is selected from the group consisting of SEQ ID NOS.: 1-9. 